Compressed air starter motor of rotary piston construction for internal combustion engines



Dec. 3, 1968 H. HECKT 3,43,860

COMPRESSED AIR STARTER MOTOR OF ROTARY PISTON CONSTRUCTION FOR INTERNAL COMBUSTION ENGINES Filed Aug. 25, 196e INVENTOR HEINZ HE DKT.

ZM im .ATTYS,

"flnited States Patent O 3,413,860 COMPRESSED AIR STARTER MOTOR OF ROTARY PISTON CONSTRUCTION FOR INTERNAL COM- BUSTION ENGINES Heinz Heckt, Holterstrasse 12a, Sprockhovel, Westphalia, Germany Filed Aug. 25, 1966, Ser. No. 575,120 Claims priority, application Germany, Aug. 31, 1965, D 48,097 4 Claims. (Cl. 74-6) ABSTRACT OF THE DISCLOSURE A compressed air starter motor of rotary piston construction having air driven rotors operatively connected to a drive pinion. The motor has an air operated meshing piston and a pinion shaft which mounts the drive pinion. A gear unit output member surrounds the pinion shaft and is operatively connected to the pinion shaft. A lever is connected between the meshing piston and the pinion shaft. Displacement of the meshing piston acting through the lever moves the pinion shaft axially. A wedge body overrunning clutch is positioned between the gear unit output member and the pinion shaft. A lost motion mechanism is connected to the lever and the meshing pinion and is effective to absorb the difference in displacement between the meshing piston displacement and the axial displacement of the pinion shaft.

This invention relates to an improved air starter motor of rotary piston construction for internal combustion engines. A compressed-air starter motor can be constructed wherein the said starter motor has rotors, which act via a gear train to drive a pinion, and a manually or pneumatically actuated control valve which in its open position connects a compressed air inlet with a cylinder chamber of a meshing piston connected with the pinion via a lever and with a narrow nozzle extending to the rotors of the motor, the meshing piston being so disposed that the entire compressed air inlet cross-section to the rotors is exposed only when the pinion is in mesh.

In such a design a compressed-air starter motor is provided which corresponds to conventional electric starters with regard to its housing dimensions and which can -be switched on by means of a single control motion for a subsequent automatic operation of the starting process and which can be switched off by hand or, if required, automatically. In the compressed air starter motor of such a design a considerably larger return force is exerted on the pinion in contrast with conventional constructions.

The compressed air starter motor in such a design operates so that initially a small amount of compressed air is supplied to the rotors via the narrow nozzle so that the rotors rotate slowly while the meshing piston moves under the effect of the inliowing compressed air and thus moves the pinion into the meshing position. If the control valve is returned into its starting position, the meshing piston will move the pinion from its meshing position and at the same time shut down any further supply of compressed air to the rotors.

Such a design does not provide any devices to separate the starter pinion and the starter motor during the overrunning phase which accompanies starting of the internal combustion engine. Therefore, the danger arises of the rotating parts of the starter being accelerated to considerable speeds due to the reduction ratio prevailing between the gear rim of the internal combustion engine and the starter pinion if timely disengagement of the pinion is not ensured. This would lead to considerable mechanical stresses being imposed on the starter motor and would in ice extreme cases lead to the complete destruction of its mechanical parts.

overrunning clutches on starter motors have already been disclosed by the prior art. In particular there are plate clutches which are compressed during starting by means of a compressing nut via a high-pitch screw thread and which are separated from each other during the overrunning phase when the compressing nut is released; the external clutch plates which have raised portions can therefore slide axially in accordance with the displacement of the pinion in longitudinal grooves of the external body. However, it has been found that such plate clutches frequently do not operate Suiciently satisfactorily and that the overrunning phase is readily accompanied by burning of the clutch plates.

It is also not new to provide starter motors with overrunning clutches of the form of free-wheeling devices whose internal and external locking ring cannot be displaced relative to the locking body, the axial motion of the pinion beng provded by a spline connection. The spline connection may also be of helical form.

It is the object of the present invention to provide a starter lmotor wherein absolutely reliable separation between pinion and starter motor is ensured when the internal combustion engine starts, that is to say during the accompanying overrunning phase.

Further objects of this invention will become apparent from the following specification and drawing, in which:

FIG. l is a longitudinal, cross sectional View of an embodiment of a starter motor constructed according to the present invention` The invention is based on the fact that certain freewheeling units can be so adjusted that they permit an axial displacement of the rotating pinion when the said pinion enmeshes before the pinion shaft is completely locked to the gear unit output shaft.

The purpose of the invention is fundamentally achieved by the provision of a wedge body clutch between the gear unit output and a shaft carrying the pinion, the pinion shaft being enmeshable against the coupling force exerted by the compressed air which flows inwards through the narrow nozzle during rotation of the rotors and by the meshing piston traversing a distance which is longer than the axial motion of the pinion shaft, the traversing displacement difference relative to the pinion displacement being absorbed by a no-load device.

The compressed air starter motor according to the invention includes starting of the rotors by means of the narrow nozzle. This is accompanied by coupling of the pinion shaft with the gear unit output and the pinion shaft is `displaced in the coupled condition to enable reliable meshing of the pinion to take place even if the pinion and the gear rim of the engine to be started are disposed in tooth opposition. The full ow of compressed air is applied to the rotors only after meshing so that the wedge bodies then fully interlock and no longer permit any axial motion of the pinion shaft. In this operating condition it is impossible for the pinion to be disengaged. Disengagement becomes possible only if the internal combustion engine has started and the overrunning phase is initiated so that the Wedge body overrunning clutch is released. To permit interruption of the starting process if the internal combustion engine does not start, the displacement which is increased relative to the axial motion of the pinion shaft enables the meshing piston to initially shut off the supply of compressed air to the rotors before the pinion is disengaged. Consequently, the wedge body overrunning clutch can be so released as to permit an axial displacement of the pinion shaft.

Among the principal advantages provided by the invention is the considerable improvement of the disengagement and engagement process previously known because the starter motor is not subjected to the high mechanical stresses if the pinion is not disengaged shortly after the internal combustion engine starts. As stated above, an important feature of the invention is the displacement of the pinion shaft While the wedge body overrunning clutch is still locked. This offers the advantage of continuous rotation of the pinion during the meshing phase so that meshing cannot be obstructed by teeth being disposed in opposition. Moreover, the overall construction of the compressed air starter motor is thus rendered very simple.

In a practical embodiment of the invention it is of course possible for the no-load or lost motion device to be constructed in different ways. It has been found particularly practical and convenient to construct the noload device as a sleeve adjoining the lever and having a collar extending into the cylinder of the meshing piston and a bolt mounted on the meshing piston and introduced into the sleeve, the said bolt being connected with the sleeve by `means of a xed pin mounted thereon and sliding in a slot of the bolt. The consequence of this 4method of construction of the no-load device is that after onset of the meshing piston movement the bolt and sleeve are pressed apart by the force differential of the compressed air acting on the sleeve collar so that the piston can, with absolute reliability, rst shut off the supply of compressed air to the rotors of the starter motor before the pinion is disengaged.

A further improvement can also be obtained in a practical embodiment of the invention in the event that the teeth of the pinion and of the internal combustion engine are in opposition during the meshing phase despite the slowly rotating rotors so that the resultant axial reaction force acting on the pinion shaft can be resiliently absorbed. This is achieved in a further embodiment of the invention in that for the purpose of absorbing axial loads of the pinion shaft during the meshing phase two trust pieces surrounding a steel ball are provided between the rotor end of the pinion shaft and the lever drive.

The invention is described in detail hereinafter by reference to a preferred embodiment, illustrated in the drawing. The drawing shows a longitudinal secion through a compressed air starter motor according to the invention having rotors 19 which act via a gear unit, whose details are not shown, to drive a pinion 7. The gear unit has an output shaft 40 which is located in the gearbox 21 in fixed bearings 41, 42.

When opened, a control valve 3, to be pneumatically actuated in accordance with the illustrated embodiment example, connects a compressed air inlet 2 with a cylinder chamber of a meshing piston 5, connected with the pinion 7 via a lever 6, and with a narrow nozzle 20 leading to the rotors 19 of the motor. The entire compressed air inlet cross-section is exposed, as will be described later, only when the pinion is fully meshed.

A wedge body overrunning clutch 24, Whose wedge bodies are known and need not be described in greater detail, are disposed between the gear unit output shaft 49 and a shaft 14 which carries the pinion 7. Rotation of the rotors 19 by means of the compressed air flowing through the narrow nozzle 20 causes a coupling force to be exerted by the wedge bodies 24 onto the pinion shaft 14 so that the pinion shaft 14 rotates with the gear unit output shaft 4G. The wedge bodies are so adjusted that the coupling force exerted by them is only large enough to enable the pinion shaft to mesh.

As will be described in detail, the lmeshing p-iston has a displacement which is larger relative to the axial motion of the pinion shaft 14, the difference of the motion relative to the pinion displacement being absorbed in a no-load device.

The starting phase is described hereinafter.

In the normal condition, entry of the compressed air to the starter is blocked by a valve plate 1. Compressed air passes via a duct in communication with an inlet chamber through the control valve 3 and from there through a duct 4 to the disengagement side of the meshing piston 5 which, while in this position, retains the pinion 7, via a lever 6, in the disengaged position, us shown in the drawing. Compressed air passing through the duct 2 to the other side acts on a venting valve 8.

By operation of a valve 9 a pipeline 10 leading from the pressurized chamber to the valve 9 is connected with a pipeline 11 which connects the valve 9 with the piston side of the control valve 3. The control valve 3 is displaced, as far as a stop, to the left against the pressure exerted by a spring 12, so that the disengaging side of the meshing piston 5 can be vented through a venting bore 13 and the opposite side can be pressurized through a bore 27. The meshing piston 5 is thus displaced and together with it the shaft 14 and the pinion 7 are displaced, via a sliding block 18 and the lever 6, into meshing relationship with a gear rim of the internal combustion engine. This process takes place against the force exerted by the Wedge bodies 24 which are already coupled.

This ensures reliable meshing of the starter pinion because while displacement takes place, the rotors 19 of the motor are pressurized with compressed air through the narrow nozzle 20 so that the pinion 7 is set into slow rotation.

Axial stresses, which could occur if the teeth of the pinion and of the gear rim 15 are in opposition, are absorbed by two thrust pieces 16 which encompass .t steel ball 17.

As already mentioned, during the meshing phase the pinion shaft is displaced through the bearings 22 which are permanently mounted in the gearbox housing 21. through the bearing 23 which are permanently mounted in the gearbox housing and through the wedge body overrunning clutch 24 which operates in the manner of a freewheeling device. In this contiguration the pinion shaft 14 represents the internal running surface of the bearings and the internal clamping surface for the wedge bodies 24. The free-wheeling device thus obtained is subjected to a slight radial loading by the slowly rotating spindle during the displacement.

At the end of the displacement the venting valve 8 is operated by a push rod connected with the meshing piston 5. A communication passage is thus provided for the compressed air through a duct 25 to a piston of a main valve 26 which in turn displaces the valve plate 1 which is carried by the piston rod. Compressed air is directed against the rotors 19. The starter thus acquires its desired speed and starts the internal combustion engine. The free-wheeling device formed by the wedge bodies 24 will then be in positive engagement and can no longer he axially displaced by the force exerted by the piston 5.

In order to complete the starting operation it is necessary either to wait until the gear rim 1S has overrun the pinion 7 so that the free-wheeling device formed by the wedge bodies 24 is released or to close the main valve l at any desired moment of time of the starting process. The last-mentioned possibility is necessary in the event that the internal combustion engine does not start and is applied as follows:

In accordance with the illustrated embodiment, the meshing piston 5 traverses a distance approximately 5 mm. longer than the corresponding axial displacement of the pinion 7 or the pinion shaft 14. During the initial disengagement phase a bolt 28 which is permanently connected to the meshing piston 5 is displaced until a lock or stop is reached. According to the illustrated embodiment a longitudinal slot 43 is provided in the bolt 28. l'he slot 43 receives a pin 44 carried in a sleeve 29. The sleeve 29 is connected with the lever 6. The parts thus described represent a no-load or lost motion device.

As soon as the bolt 28 and the sleeve 29 are separated from each other, from the position indicated in the drawing, the bolt 28 and sleeve 29 are pressed apart by the differential force ofthe compressed air acting on the sleeve collar 45.

To terminate the starting phase, the valve 9 must be moved into the zero position whereupon the pipeline 11 is vented and the control valve 3 is pushed back into its starting position by the force exerted by the spring 12. As a result, the side of the meshing piston 5, which is pressurized during starting, is vented through a duct 27. At the same time, the opposite side of the meshing piston 5 is pressurized and the meshing piston is displaced until the stop side of the bolt 28 meets the sleeve collar 45 of the sleeve 29. This displacement enables the venting valve 8 to close and the main valve 1 closes as the result of the spring force. Thereafter, the frictional engagement between the free-wheeling device 24, formed by the wedge bodies, and the pinion shaft 14 is released. From this moment of time onwards the meshing piston 5 will begin to disengage the pinion until the starting condition is regained on completion of the disengagement displacement.

While the present invention has been disclosed with respect to a specific disposition of parts, many changes and modifications may be made to the disclosed embodiment without departing from the scope of the appended claims.

I claim:

1. In a compressed air starter motor of rotary piston construction having air driven rotors operatively connected to a drive pinion, the invention comprising, in combina tion, an air operated meshing piston, a pinion shaft mounting said drive pinion, a gear unit output member operatively connected to such rotor and coaxially mounted with respect to at least a portion of said pinion shaft, a lever operatively connected between said meshing piston and said pinion shaft, whereby displacement of said meshing piston is effective to move said pinion shaft axially, a wedge body overrunning clutch positioned between said gear unit output member and said pinion shaft, and lost motion means connected to said lever and said meshing piston elective to absorb the difference in displacement between the meshing piston displacement and the axial displacement of the pinion shaft.

2. A compressed air starter motor, according to claim 1, wherein said lost motion means comprises a sleeve member connected to said lever, said sleeve member having a collar extending into the cylinder of said meshing piston, a bolt mounted on said meshing piston, said bolt defining a slot therethrough and being positioned for movement Within said sleeve, a pin extending transversely across internally of said sleeve, said pin being received by such bolt slot, whereby said bolt is connected by said sleeve and is slidably mounted Within said sleeve.

3. A compressed air starter motor, according to claim 1, including thrust means comprising thrust pieces encompassing a metallic ball positioned between the motor end of said pinion shaft and said lever, said thrust means being effective to absorb axial stresses imposed on said pinion shaft during meshing.

4. A compressed air starter motor, according to claim 2, including thrust means comprising thrust pieces encompassing a metallic ball positioned between the motor end of said pinion shaft and said lever, said thrust means being effective to absorb axial stresses imposed on said pinion shaft during meshing.

References Cited UNITED STATES PATENTS 6/1955 Jenny 123-179 5/1965 Heckt 123-1'79 

